Telescopic boom with a multistage, lockable hydraulic cylinder protected against buckling

Abstract

A telescopic boom with a multistage, lockable hydraulic cylinder is provided with a protection against lateral buckling of the hydraulic cylinder, said hydraulic cylinder being supported by the more rigid boom members (telemembers). For this purpose, a multipart supporting device is provided, one part of said supporting device being secured to at least one unit of the multistage hydraulic cylinder and the other part thereof being secured to the inner wall of the at least one telemember. The two parts of the supporting device are continuously in engagement with one another so that the desired protection against buckling of the hydraulic cylinder will be guaranteed at all positions of the boom. Furthermore, suitable measures guarantee that, starting with the cylinder unit having the largest cross-section, it is always the cylinder unit having the next smaller cross-section which, in an orderly sequence, is first fully extended, the reverse order being observed during the retraction process. A particular advantage of the present invention is to be seen in the fact that hydraulic fluid can in each case only be supplied to the cylinder chamber of a cylinder unit which has already reached its fully extended position, since a check valve is still closed in all the subsequent cylinder units so that these cylinder units cannot be extended for the time being. This check valve will only open when the cylinder unit occupies its fully extended position.

I claim: 
     
       1. A telescopic boom having boom members and cylinders units, comprising: (a) a non-displaceable boom member;   (b) at least one displaceable boom member, connected to said non-displaceable boom member and telescopically displaceable with respect to the non-displaceable boom member;   (c) a non-displaceable cylinder unit, connected to the non-displaceable boom member and housed within the non-displaceable boom member;   (d) at least one displaceable cylinder unit connected to said non-displaceable cylinder unit and telescopically-displaceable with respect to said non-displaceable cylinder unit, said at least one displaceable cylinder unit being connected to said at least one displaceable boom member for telescopically displacing the at least one displaceable boom member with respect to the non-displaceable boom member, the at least one displaceable cylinder unit having a fully extended position, a fully retracted position, and a piston head for hydraulically separating the at least one displaceable cylinder unit from the non-displaceable cylinder unit, the piston head being located at an end face of said at least one displaceable cylinder unit, the piston head having a first transfer port for allowing fluid flow through the piston head between the non-displaceable cylinder unit and the at least one displaceable cylinder unit, a first check valve connected to the first transfer port for restricting fluid flow through the transfer port, and a first actuating element connected to the first check valve for opening the check valve when the at least one displaceable cylinder unit is in the fully extended position;   (e) a supporting device having a first component attached to at least one of the at least one displaceable cylinder unit and the non-displaceable cylinder unit, and having a second component attached to at least one of the at least one displaceable boom member and the non-displaceable boom member, the second component supporting the first component so that the boom members support the cylinder units; and   (f) a locking means connected to the at least one displaceable cylinder unit for releasably locking the at least one displaceable cylinder unit in the fully extended position.   
     
     
       2. The telescopic boom of claim 1 wherein the first component of the supporting device comprises a first claw and a second claw and wherein the second component of the supporting device comprises a first rail and a second rail, the first claw enclosing the first rail and the second claw enclosing the second rail. 
     
     
       3. The telescopic boom of claim 2 comprising at least two displaceable boom members including at least one intermediate displaceable boom member and a distal displaceable boom member, wherein there is more than one said supporting device so that each boom member has a corresponding supporting device connected thereto, wherein said first component is attached to a corresponding cylinder unit and said second component is attached to a corresponding boom member, and wherein said at least two displaceable boom member are inner boom members telescopically-receivable within said non-displaceable boom member, said first and second rails of each of the at least two displaceable boom members including an inner first rail and an inner second rail, respectively, said distal displaceable boom member having an inner first rail extending the length of the distal displaceable boom member and an inner second rail extending the length of the distal displaceable boom member. 
     
     
       4. The telescopic boom of claim 3 wherein each said first claw engages a corresponding inner first rail and each said second claw engages a corresponding inner second rail when the telescopic boom is fully retracted. 
     
     
       5. The telescopic boom of claim 3 comprising a plurality of intermediate displaceable boom members, wherein the first rail and the second rail of each supporting device of each intermediate displaceable boom member are shorter than the corresponding boom member in which said rails are connected. 
     
     
       6. The telescopic boom of claim 3 wherein all first rails extend in planar alignment with each other and wherein all second rails extend in planar alignment with each other. 
     
     
       7. The telescopic boom of claim 1 wherein the at least one displaceable cylinder unit is connected to at least one displaceable boom member so that the at least one displaceable boom member moves simultaneously with the at least one displaceable cylinder unit. 
     
     
       8. The telescopic boom of claim 6 wherein each displaceable cylinder unit is connected to a corresponding displaceable boom member so that each displaceable boom member moves simultaneously with a corresponding displaceable cylinder unit. 
     
     
       9. The telescopic boom of claim 7 wherein the at least one displaceable cylinder unit is connected to the at least one displaceable boom member by tie rods. 
     
     
       10. The telescopic boom of claim 8 wherein each displaceable cylinder unit is connected to a corresponding displaceable boom member by tie rods. 
     
     
       11. A telescopic boom having boom members and cylinder units, comprising: (a) a non-displaceable boom member;   (b) a plurality of displaceable boom members, connected to said non-displaceable boom member and telescopically-displaceable with respect to the non-displaceable boom member, said plurality of displaceable boom members including at least one intermediate displaceable boom member and distal displaceable boom member;   (c) a non-displaceable cylinder unit, connected to the non-displaceable boom member and housed within the non-displaceable boom member;   (d) a plurality of telescopically-displaceable cylinder units connected to corresponding displaceable boom members of said plurality of said displaceable boom members, including at least one intermediate displaceable cylinder and a distal displaceable cylinder unit, the at least one intermediate displaceable cylinder unit comprising a first displaceable cylinder unit connected to said non-displaceable cylinder unit and telescopically-displaceable with respect to said non-displaceable cylinder unit, said first displaceable cylinder unit being connected to said at least one intermediate displaceable boom member for telescopically displacing the at least one intermediate displaceable boom member with respect to the non-displaceable boom member, the first displaceable cylinder unit having a fully extended position, a fully retracted position, and a piston head for hydraulically separating the first displaceable cylinder unit from the non-displaceable cylinder unit, the piston head being located at an end face of said first displaceable cylinder unit, the piston head having a first transfer port for allowing fluid flow through the piston head between the non-displaceable cylinder unit and the first displaceable cylinder unit, a first check valve connected to the first transfer port for restricting fluid flow through the first transfer port, a first non-return valve cooperating with the first check valve for allowing fluid flow through the first transfer port in one direction only, a first actuating element connected to the first check valve for opening the first check valve when the first diplaceable cylinder unit is in the fully extended position, a second transfer port for allowing fluid flow through the piston head between the non-displaceable cylinder unit and the first displaceable cylinder unit, a second check valve connected to the second transfer port for restricting fluid flow through the second transfer port, a second non-return valve cooperating with the second check valve for allowing fluid flow through the second transfer port in one direction only, a second actuating element connected to the second check valve for opening the second check valve when a second displaceable cylinder unit of said plurality is in a fully retracted position, said second displaceable cylinder unit being connected to said first displaceable cylinder unit and telescopically-displaceable with respect to said first displaceable cylinder unit;   (e) closeable recirculating line means connected to the distal displaceable cylinder unit for allowing hydraulic fluid flow out of each said cylinder unit through each respective second transfer port; and   (f) a supporting device having a first component attached to at least one of the first displaceable cylinder unit and the non-displaceable cylinder unit, and having a second component attached to at least one of the at least one intermediate displaceable boom member and the non-displaceable boom, the second component supporting the first component so that the boom members support the cylinder units.   
     
     
       12. The telescopic boom of claim 1 wherein said at least one displaceable cylinder unit comprises an annular shoulder for engaging a corresponding first actuating element, and wherein said corresponding first actuating element comprises an actuator ring for engaging the corresponding annular shoulder, a rod for connecting the corresponding actuator ring to the corresponding first check valve, and a spring for biasing the corresponding actuator ring so that the corresponding first check valve is closed. 
     
     
       13. The telescopic boom of claim 11 wherein each of said displaceable cylinder units further comprise an annular shoulder for engaging a corresponding first actuating element, and wherein said corresponding first actuating element comprises an actuator ring for engaging the corresponding annular shoulder, a rod for connecting the corresponding actuator ring to the corresponding first check valve, and a spring for biasing the corresponding actuator ring so that the corresponding first check valve is closed. 
     
     
       14. The telescopic boom of claim 1 further comprising a restoring cable connected to said at least one displaceable cylinder unit for retracting the telescopic boom and a winch connected to said restoring cable for retracting the restoring cable. 
     
     
       15. The telescopic boom of claim 11 further comprising a restoring cable connected to said distal displaceable cylinder unit for retracting the telescopic boom and a winch connected to said restoring cable for retracting the restoring cable. 
     
     
       16. The telescopic boom of claim 14 wherein the winch is driven by a hydraulic motor which is connected to a lowering braking valve for controlling a driving speed of the winch. 
     
     
       17. The telescopic boom of claim 15 wherein the winch is driven by a hydraulic motor which is connected to a lowering braking valve for controlling a driving speed of the winch. 
     
     
       18. The telescopic boom of claim 16 wherein the winch is connected to a biasing spring so that the restoring cable is constantly tensioned. 
     
     
       19. The telescopic boom of claim 17 wherein the winch is connected to a biasing spring so that the restoring cable is constantly tensioned. 
     
     
       20. The telescopic boom of claim 11 wherein the first component of the supporting device comprises a first claw and a second claw and wherein the second component of the supporting device comprises a first rail and a second rail, the first claw enclosing the first rail and the second claw enclosing the second rail. 
     
     
       21. The telescopic boom of claim 20 comprising at least two displaceable boom members including at least one intermediate displaceable boom member and a distal displaceable boom member, wherein there is more that one said supporting device so that each boom member has a corresponding supporting device connected thereto, wherein said first component is attached to a corresponding cylinder unit and said second component is attached to a corresponding boom member, and wherein said at least two displaceable boom members are inner boom members telescopically-receivable within said non-displaceable boom member said first and second rails of each of the at least two displaceable boom members including an inner first rail and an inner second rail, respectively, said distal displaceable boom member and an inner first rail extending the length of the distal displaceable boom member and an inner second rail extending the length of the distal displaceable boom member.